CH 4 Key Words Flashcards
Transmembrane Domain
The portion of a membrane protein that passes through the the lipid balayer, often composed of non-polar amino acids in an alpha-helical conformation
Head Group
The polar, water-soluble regions of a phospholipid that consists of a phosphate group linked to one of several small, hydrophilic molecules
Ligand-Gated Channel
A membrane channel that opens or closes in response to binding of a molecule to its surface
Antiport
A mode of membrane transport in which one transported species is moved across the membrane in one direction, coupled with the motions fo a different species across the membrane in the opposite direction
Facilitative Transporter
A transmembrane protein that binds to a specific substance and, in doing so, changes conformation to facilitate diffusion of the substance down its concentration gradient
Hypertonic
Property of one compartment having a higher solute concentration compared with that in a given compartment
Phosphoglycerides
The name given to membrane phospholipids that are built on a glycerol backbone
Active Transport
The energy requiring process in which a substance binds to a specific transmembrane protein, changing its conformation to allow passage of the substance through the membrane against the electrochemical gradient for that substance
Ligand
Any molecule that can bind to a receptor because it has a complementary structure
Receptor
Any substance that can bind to a specific molecule (ligand), often leading to uptake or signal transduction
Semipermeable
The membrane property of being freely permeable to water while allowing much slower passage to small ions and polar solutes
Phospholipids
Phosphate containing lips that represent the primary constituents of the lipid bilayer of cellular membranes. Phospholipids include both phosphoglycerides and sphinomyelin
GPI-anchored Proteins
Peripheral membrane proteins that are anchored to the membrane via linkage to a glycosylphosphatidylinositol molecule of the bilayer
Alkylating Agent
A chemical that reacts with a protein to attach a linear or branched hydrocarbon chain onto the protein
Plasmolysis
The shrinkage that occurs when a plant cell is placed into a hypertonic medium; its volume shrinks as the plasma membrane pulls away from the surrounding cell wall
Voltage-sensing Domain
The portion of a voltage-gated ion channel that allows it to respond to membrane voltage
Facilitated Diffusion
Process by which the diffusion rate of a substance in increased through interaction with a substance-specific membrane protein
Signal Transduction
The overall o process in which information carried by extra cellular messenger molecules is translated into changes that occur inside a cell
Peripheral Proteins
A membrane-associated protein that is located entirely outside of the lipid bilayer and interacts with it through non covalent bonds
Conductance
The movement of small ions across membranes
Lipid Bilayer
Phospholipids self-assembled into a i molecular structure based on a hydrophobic and hydrophilic interactions; biologically important as the core organization of cellular membranes
Transition Temperature
The temperature at which a membrane is converted from a fluid state to a crystalline gel in which lipid-molecule movement is greatly reduced
Plasma Membrane
The membrane serving as a boundary between the interior of a cell and its extra cellular environment
Single-Particle Tracking (SPT)
A technique for studying movement of membrane proteins that consists of 2 steps
(1) linking the protein molecules to visible substances such as colloidal gold particles
(2) monitoring the movements of the individual tagged particles under the microscope
Liposome
An artificial lipid bilayer that self-assembles into a spherical vesicles or vesicle when in an aqueous environment
Electrochemical Gradient
The overall difference in electrical charge and in solute concentration that determines the ability of an electrolyte to diffuse between two components
Partition Coefficent
The ratio of a solutes solubility in oil to that in water, it is a measure of the relative polarity of a biological substance
Pore Domain
The part of a voltage-gated ion channel that forms an ion-conducting channel through the membrane
Gated Channel
An ion channel that can change conformation between a form open to its solute ion and one closed to the ion; such channels can be voltage gated, chemical gated, or mechanically gated depending on the nature of the process that triggers the change in conformation
Saturation
A condition in which every molecule of an enzyme or transporter is bound with its substrate molecule, so that adding more substrate has no additional effect on the rate of reaction or transport
Sphingolipids
A class of membrane lipids -derivations of sphingosine- that consist of sphingosine linked to a fatty acid by its amino group
Symport
Simultaneous transport of two chemical species in the same direction by a single transporter
Lipid Rafts
Micro domains within a cellular membrane that possess decreased fluidity due to the presence of cholesterol, glycolipids, and phospholipids containing longer, saturated fatty acids. A proposed residence of GPI-anchored proteins and signalling proteins
Glycolipids
Sphingosine-based lipid molecules linked to carbohydrates, often active components of plasma membranes
Glycosylation
The reactions by which sugar groups are added to proteins and lipids
Mechano-gated Channel
A membrane channel that opens or closes in response to mechanical forces such as tension in the membrane
Hypotonic
Property of one compartment having a lower solute concentration compared with that in a given compartment
Osmosis
The property of water passing through a semipermeable membrane from a region of lower solute concentration to one of higher solute concentration, with the tendency of eventually equalizing solute concentration in the two compartments
Voltage-Gated Channel
An ion channel that opens or closes in response to changes in the voltage across a membrane
Integral Protein
A membrane-associated protein that penetrates or spans the lipid bilayer
Cotransport
A process that couples the movement of two solutes across a membrane, termed support if the two solutes are moved in the same direction and antiport if the two move in opposite directions
Ion Channel
A transmembrane structure (eg. An integral protein with an aqueous pore) permeable to a specific ion or ions
Lipid-anchored Protein
A membrane associated protein that is located outside the bilayer, but is covalently linked to a lipid molecule within the bilayer
Isotonic
Property of one compartment having the same solute concentration compared with that in a given compartment
Cell Fusion
Technique whereby two different types of cells (from one organism or from different species) are joined to produce one cell with one, continuous plasma membrane
Freeze-Fracture Replication
Technique in which a tissue sample is first frozen and then struck with a blade that fractures the tissue block along the lines of least resistance, often resulting in a fracture line between the two leaflets of the lipid bilayer; metals are then deposited on the exposed surfaces to create a Shawnee replica that is analyzed by electron microscopy
Transmembrane Protein
A protein that is inserted into a membrane and spans across the whole width of the membrane
Diffusion
The spontaneous process in which a substance moves from an area of higher concentration one of lower concentration, eventually reaching the same concentration in all areas
Cholesterol
Sterol found in animal cells that can constitute up to half of the lipid in a plasma membrane, with the relative proportion in any membrane affecting its fluid behaviour
